Contrasting effects of waste glass and scheelite tailings additions upon the properties of tailings-based foam ceramics and its mechanisms

Although solid waste is a good raw material for preparing foam ceramics, the mechanisms of the discrepancies in different solid wastes affecting the properties of foam ceramics remain unelucidated. In this study, the properties of tin tailings-based foam ceramics with different proportions of waste glass (WG) or scheelite tailings (ST) were measured. Significant discrepancies in the influence effects were observed, with higher closed porosity for added WG and higher apparent porosity for added ST. To interpret this phenomenon, the effects of the main fluxing agents of the ST and WG were investigated, and the results indicated that their influence effects were controlled by the type and content of the fluxing agent. Furthermore, the structure and crystalline phase of foam ceramics demonstrated that their compressive strength was jointly driven by their microstructure and crystal phases, but other properties depended only on the microstructure. The pore size and type were significantly affected by the change in liquid phase characteristics and aluminosilicate, with the addition of WG dramatically decreasing the number of pore windows and the addition of ST increasing the content of anorthite. Further sintering process analysis results revealed that the chemical reactions in materials change with chemical compositions, which resulted in significant differences in the crystalline compositions of the foam ceramics for WG and ST additions, and the presence of WG obviously reduced the formation temperature of the liquid phase. Overall, our research provides a theoretical basis for better utilizing different solid wastes to prepare foam ceramics.